38 weber tochev 4.1

Post any technical questions, FAQs or tutorials in this section
Post Reply
PappaD
Posts: 6
Joined: Wed 31 May 2017, 10:48

38 weber tochev 4.1

Post by PappaD » Wed 31 May 2017, 11:27

Hi guys,
I have just fitted a 38 weber carb to my Chev C10 4.1 engine using an adaptor on the standard intake. The engine idle fine but has got a bad flatspot(backfires through the carb) when accelerating. It gets better when I advance the timing. Currently on 12 degrees before but the flatspot is still there but less backfiring.
I have new gasgets between carb and adaptor etc. I fitted 210 air jets with 137 mains. Carb is clean. I have replaced the diaframe on the accelerator pump thinking it might under deliver causing the flatspot...still the same.
Yesterday I discovered that closing the airjets on both sides doesn't really makes a differance. To my knowledge the engine should stall.
I was thinking an airleak but the gasgets are new and seems to seal properly by the look of the inprint of everything on the gasgets. I even sprayed some carbcleaner on the base and inlet gasget by the head side to see if it makes a differance, mabe sucking some in if a gasget is not sealing properly, thinking this will bring a change when idling. Nothing noticable.
Question: Can this be because of wrong jetting? Can the air its getting through the valvecover pipe to the manifold cause this? Is there anything I missed that should be done with such an conversion? Maybe my distributor?
Thanx for any advice and suggestions. D

User avatar
Johann66
Posts: 245
Joined: Fri 14 Apr 2017, 13:21

Re: 38 weber tochev 4.1

Post by Johann66 » Wed 31 May 2017, 14:03

Take a search on this Forum. Did some weber conversion on the 4.1 Chev engine! Ridgeback was the receiver!

User avatar
ters
Posts: 4202
Joined: Thu 19 Jan 2012, 19:39
Location: Pretoria

Re: 38 weber tochev 4.1

Post by ters » Wed 31 May 2017, 18:36

Welcome pappa. Please introduce yourself? http://africanmusclecars.com/forum/viewforum.php?f=41 Tell us about yourself, show some pics of your C? Which area are you from...makes it easy advising where to search for help/spares....

Ters.
When it comes to the wife its easier to beg for forgiveness than ask for permission!
AMC Forum now accessible on Tapatalk! http://www.tsclassicclinic.co.za/

PappaD
Posts: 6
Joined: Wed 31 May 2017, 10:48

Re: 38 weber tochev 4.1

Post by PappaD » Wed 31 May 2017, 21:36

Thanx Johann66 I did and learned alot.
I did however got the engine to stall when fully closing the airscrews. I fitted an extra adaptor so to speak with a "W" shaped plate that hangs from it in the manifold to help with the air/fuel distribution. Now this had an small 3mm hole for an extra vacuum pipe I think. I blocked it and wala.
Something interesting. The engine still had a terrible flatspot and backfired through the carb.
After coffee and staring at the car for 30 minutes I had the thought of checking the timing marks.
Removed no.1 sparkplug, entered a screwdriver to feel the piston coming up and got the engine on TDC by means of the screwdriver.
The TDC mark on the pully was out with about 14 degrees. So on 12 BTDC where I had her instead of the normal 6, timing was actually still 2 degrees ATDC.
The rubber on the crankpully, inbetween the 2 parts of the pully, this must be totally vrot and busy allowing the outer section to slip on the inner part....
I will remove the pully tomorrow and confirm my statement but the bakkie runs prettymuch the way she should now, no more backfire and flatspot.
Now fancy that 😃

PappaD
Posts: 6
Joined: Wed 31 May 2017, 10:48

Re: 38 weber tochev 4.1

Post by PappaD » Wed 31 May 2017, 21:44

Thanx Ters, I did introduce myself just now. I do not have my computer with me so I am posting from my phone and battle to find all the buttons to upload some pics. I will keep on trying 😉

User avatar
Johann66
Posts: 245
Joined: Fri 14 Apr 2017, 13:21

Re: 38 weber tochev 4.1

Post by Johann66 » Wed 31 May 2017, 22:02

Glad the info was of use! The rubber insert in the crank pully does go after time! I have such a vrot pully already in two pieces! Good luck!

Ridgeback
Posts: 143
Joined: Tue 04 May 2010, 11:12
Location: Pietersburg/Polokwane

Re: 38 weber tochev 4.1

Post by Ridgeback » Thu 01 Jun 2017, 17:24

Hi and welcome
The pulleys on the 4.1 get hard and crack and move.
Try the following
Mark distribitor shaft with a pencil and also base plate so you know where you started.
Start engine and get it warm. Get motor to run around 1500-2000 revs
Now loosen base plate nut and turn distributor anti clock until emgine wants to cut - mark this point
Now turn anti clock ways until motor wants to cut - mark again
Now find middle point of the 2 marks then turn again the dizzy until this middle mark and engine is running smothly.
This is very basic but will help. You can still play around this middle mark

If you dont come right look this site up posted by one of our members.
http://classicinlines.com/vacuum.asp. All to do of how to tune with vacuum gauge. Very handy
BEST OF LUCK
Ridgeback

Post Reply

Social Media

     

Who is online

Users browsing this forum: No registered users and 1 guest